The present invention relates to a lifting device for holding and locking rope under tension. More particularly, the present invention relates to a lifting device having a self locking feature upon release of a first end of a line, so that a load on the second end of the line will not be freed, except by operation of the first end of the line when placed under tension.
Cam cleats for releasably clamping and holding ropes are well known in the art, with prior art patents dating back over a century. For particular rope holding and adjusting applications, however, even the populous prior art has left various problems unresolved.
Cam cleats are widely used on sailing vessels and the like, and generally comprise one or more spring loaded pawls which serve to releasably lock a line or rope in one direction, namely the direction of the load on the line. The free end of the line can be pulled manually through the cam jaws or pawls, and the line is locked when tension is released on the free end of the line. The line can be disengaged only by manually lifting the line out of engagement with the pawl. It is also generally known to provide a retaining member above the pawls to constrain the line after it has been released, which facilitates re-engagement of the line with the cam. Many examples of known cam cleats are described in the 1999 Harken Yacht Fittings catalog published by Harken, Inc., Pewaukee, Wis.
Cam cleats having a lever arm on one of the cams are also known. The free end of the line can be deflected against the lever arm to release the associated cam.
Notwithstanding past development, however, there presently exists a need for a fail safe device for raising and lowering heavy objects. As an example, for storage in the ceiling space of a garage.
The present invention solves these and other problems that remain otherwise heretofore unresolved.
It is an object of the invention to provide a lifting device having a mechanical advantage and a releasable cleat to enable fail safe raising and lowering of objects.
The present invention generally comprises a lifting device for mounting on a surface, the lifting device having an adjustable cleat and at least one pulley. A rigid frame member connects the pulley and the cleat to one another, as well as to a base, which is connected to a surface. The adjustable cleat of the lifting device has a rope engaging surface and a movable pawl. The movable pawl has a rope locking surface and a pawl arm, with the rope locking surface opposite the cleat rope engaging surface. A rope is releasably locked in place between the rope locking surface and the rope engaging surface when the movable pawl is in a closed position. The pawl may be moved into and out of locking engagement with the rope by manipulation of the pawl arm. The pulley has a sheave rotatable about a central hub, with the central hub connected to the frame member. The rope passes from the adjustable cleat and over the pulley sheave.
In operation, the rope may be urged against the pawl arm to disengage the cleat, thereby releasing the rope for adjustment. Once the rope is no longer urged against the pawl arm, a spring means urges the pawl back into a closed position, thereby locking the rope in place once again.
In a first example embodiment of the lifting device of the invention, the adjustable cleat of the lifting device of the invention comprises a rotatable pawl mounted within a U-shaped sleeve. The closed end wall of the U-shaped sleeve comprises the cleat rope engaging surface. The rotatable pawl is held between the opposing arms of the open end of the U-shaped sleeve, with the pawl rope locking surface opposite the rope engaging surface. The rope may thereby be locked in place within the sleeve. When the pawl is disengaged by urging the rope against the pawl arm, the rope is freed for adjustment through the sleeve, but remains captive within the sleeve. The pawl is preferably spring loaded and urged towards a closed position, so that upon release of the rope the pawl will move to a closed position thereby releasably locking the rope in place.
In additional embodiments of the lifting device of the invention, a plurality of pulleys are present to provide increased lifting power. An auxiliary pulley is connected to a load to be lifted. The rope may be reeved through the pulleys to provide various ratios of lifting power.
The base of the lifting device of the invention may be mounted to a vertical surface, such as a wall, or to an overhead surface such as a ceiling. In an example embodiment of the lifting device of the invention, the base comprises a hanging bail and is pivotally connected to an overhead surface. This allows for rotation of the frame holding the pulleys and pawl so as to find its static balance point under operation. Also, this allows for a user vertically below the lifting device to be located a horizontal distance away so as to not be below a suspended load.
The above brief description sets forth rather broadly the more important features of the present disclosure so that the detailed description that follows may be better understood, and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the disclosure that will be described hereinafter which will form the subject matter of the claims appended hereto. In this respect, before explaining a preferred embodiment of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments, of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. In addition, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.